Torque wrench

ABSTRACT

A torque wrench is provided of the type which comprises a yieldable beam having a work-engaging head at one end and a force-applying handle at the other end. The wrench is provided with an electrical signal circuit which preferably includes a battery and a buzzer or other signalling device, both of which may be in the handle, a reference-torque contact and an adjustable selection-torque contact. These contacts are normally open but become closed by the bending of the yieldable beam when the selected torque force is reached, thereby actuating the buzzer or other signalling device.

United States Patent Kraus 51 May 23, 1972 54] TORQUE WRENCH FOREIGN PATENTS OR APPLICATIONS [72] Inventor: Robert J. Kraus, 5 Beverly Ave., Malvern, 737,944 10/1955 Great Britain ..8l/52.5 Pa. 19355 770,611 3/1957 Great Britain ..8l/52.5

[22] Filed: July 1970 Primary ExaminerCharles A. Ruehl [21] App1.No.: 56,309

[ ABSTRACT 52 US. Cl ..73 139, 81/525 A tOrque Wrench is Provided of the yp which comprises a [51] Int. Cl. ..G01l 5/24 yieldable beam having a Work-engaging head at one end and a 58 new inseam... ..73/1 0, 139; 81/525 force-applying handle at the Other The Wrench is P vided with an electrical signal circuit which preferably in- 56] References Cited cludes a battery and a buzzer or other signalling device, both of which may be in the handle, a reference-torque contact and UNITED STATES PATENTS an adjustable selection-torque contact. These contacts are normally open but become closed by the bending of the 2,242,613 5/1941 Mandl ..73/139 yieldable beam when the Selected torque force i reached, 2,289,238 7/1942 Brunelle ..73/139 X thereby actuating the buzzer or other signalling device. 2,231,240 2/1941 Zimmerman ..73/139 2,225,420 12/1940 Mandl ..73/139 2 Claim, 9 Drawing figures FATENTEDMAY 23 I972 SHLET 1 BF 2 INVENTOR.

Robert J. Kruus PATENTEDmmzs I972 SHEET 2 [IF 2 INVENTOR.

Robert J. Krous TORQUE WRENCH BACKGROUND OF THE INVENTION The present invention relates to torque wrenches of the type shown in US. Pat. No. 3,274,827 granted to L. A. Sturtevant. This type of torque wrench includes a yieldable beam having a work-engaging head at one end and force-applying handle means at the other. Fixed to the work-engaging head is a pointer which functions as a reference. Fixed to the force-applying handle end is a calibrated scale (calibrated in footpounds or inch-pounds). As the work, which may be a bolt, nut, stud or other item, becomes tightened by the operator, the yieldable beam bends, and the calibrated scale, which is fixed to the handle end, moves laterally in an arcuate path relative to the reference pointer. The operator watches the scale and pointer, and when the desired amount of torque force is applied, he discontinues further application of force. Such torque wrenches are used in automotive maintenance work, or other work, frequently under conditions which make it difficult for the operator to see and read the scale as he tightens the work.

SUMMARY OF THE INVENTION An object of the present invention is to provide a torque wrench of the type referred to above in which the operator is relieved of the necessity of watching the scale and pointer.

Another object is to provide a torque wrench of the above type in which the operator is notified by an audio or visual signal that the desired torque force has been applied.

Another object is to provide a torque wrench of the above type which may be readily set to the value of torque force desired.

Another object is to provide a torque wrench of the above type which is relatively inexpensive to manufacture, yet is reliable in operation.

Another object is to provide a portable torque wrench of the type indicated above having a battery-operated signalling circuit which is effective to notify the operator when the desired torque force has been applied.

Another object is to provide a torque wrench of the audio signal type described above which, in the event of battery failure, can still be used as a torque wrench of the visual scalereading type.

A further object is to provide a torque wrench which is more precise and more accurate than prior art torque wrenches of the type described.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 may be considered to be a front elevational view of a torque wrench embodying one form of the present invention;

FIG. 2 is an enlarged sectional view of the torque wrench taken along the line 2-2 of FIG. 1;

FIG. 3 is an exploded view showing the various elements which are located on the axis about which the adjustable torque-setting contact arm is pivoted;

FIG. 4 illustrates a modified form of adjustable torque set contact arm and indicator plate;

FIG. 5 is a sectional view looking along the line 55 of FIG.

FIG. 6 is a side elevational broken view of a modified form of wrench;

FIG. 7 is an enlarged view, in section, looking along the line 7-7 of FIG. 6;

FIG. 8 is a schematic diagram of the electrical circuit of a still further modification;

FIG. 9 shows another modification.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 1 and 2, the wrench is shown to comprise a yieldable beam 20, having at one end a head 10 having fixed thereto a member 12 which is adapted to be received within a socket S of a proper size to engage a bolt,

stud, nut, or other work element. At the other or handle end of the beam 20 is a sleeve 40 having a threaded upper end 41 for receiving a handle 42. Sleeve 40 is illustrated as having a flat surface 40a on one side thereof to provide room for movement of the adjustable torque-set arm 30, as will be described. The sleeve 40 and the handle 42 function as the force-applying members. The beam 20, the head 10, and the force-applying members 40 and 42, are all part of the electrical signalling circuit and hence are all formed of electrically-conductive metal, preferably steel.

The yieldable beam 20 has a hollow axial bore 21 which extends from the force-applying or handle end of the beam downwardly for a short distance. Note that in FIG. 2 the beam 20 is broken, and that, as viewed in FIG. 1, the axial bore 21 extends down to about the apex of the pie-shaped indicator plate 32. At or near the lower end of the bore 21, a tapped radial hole 22 is provided. Fitted into the radial tapped hole 22 is a laterally extending metal support stud 23. As best seen in FIG. 3, lateral support stud 23 is generally cylindrical, with a flat upper surface 24, an axial bore 25, and a threaded reduced-diameter end 26 which is received within the tapped hole 22. A slot 27, provided in the flat surface 24, communicates with the axial bore 25 of the support 23.

Fitted over and supported on support stud 23, as indicated in the exploded view in FIG. 3, are a series of elements, which in order, beginning with the element closest to the beam 20, are as follows: an insulator spacer 28, an annular metal terminal 29, the annular end of the metal torque-set arm 30, an insulator spacer 31, the lower end of the pie-shaped indicator plate 32 having thereon an insulator facing 33, and a nut 34. The lower end portion of indicator plate 32 is bent, as at 132, and has a hole therethrough for receiving an insulator screw 36 for fastening the lower end 132 of the plate 32 to the beam 20. An insulator 37 is placed between the plate end 132 and the beam 20 to electrically insulate the indicator plate 32 from the beam 20. Of the component parts just described, the insulator elements; such as 28, 31, 33, 34, 36 and 37, may be plastic, while the elements 23, 29, 30, 32 and 132 may be steel or other electrically-conductive metal.

The axial bores of insulator elements 28 and 31 are provided with flats which mate with the flat surface 24 of the support stud 23. Thus, elements 28 and 31 are not rotatable on the stud 23. Insulator element 31 has a projection 131 which projects inwardly beyond the annulus of torque-set arm 30. Projection 131 has a flat upper surface which mates with the flat of the axial bore of ring terminal 29. Thus, ring terminal 29 is not rotatable on stud 23. Torque-set arm 30 has no flat surface and is rotatable or pivotal on stud 23. Indicator plate 32 is supported against pivotal movement relative to the beam 20 by reason of the combination of screw 36 into beam 20 and the projection of stud 23 through a hole in the plate 32 above the screw.

Indicator plate 32 is shown as generally pie-sector shaped, and, in the embodiment shown in FIG. 1, the upper portion of the plate is provided with a series of apertures arranged in an arcuate path. The torque-set arm 30 is provided at its upper end with a forwardly projecting head 38, and below head 38, at the level of the apertures 35 in the plate 32, the arm 30 is provided with a forwardly-projecting set finger 39 adapted to project through one of the apertures 35, as selected by the operator.

Fixed to the head 10 and extending upwardly therefrom, and parallel to the axis of the beam 20 when the beam is not bent, is a pointer of conductive metal. The upper end of the pointer 50 is adapted to be engaged by the finger 39 which extends forwardly from arm 30. A metal retaining band 51 having an insulator covering 52 extends across the indicator plate 32 and is secured to the plate 32 at each side, as by screws Band 51 retains the pointer 50 sufficiently close to the indicator plate 32 to assure that contact is made between finger 39 and the pointer 50 when the selected value of torque force has been applied.

The steel handle 42 is open at its upper end and has therein a compartment for receiving a battery 43 and a signal device, which may preferably be a buzzer 44. The open upper end of the handle 42 is threaded and is closed by a metal cap 45. One terminal 46 of battery43 is connected to an insulated wire conductor 47 which extends down through the bore 21 in the upper end of beam to the metal ring 29 on stud 23. The other terminal 48 of battery 43 is connected by a spring element to one terminal of buzzer 44 The other terminal of buzzer 44 is connected by a screw 49 to the metal cap 45. A suitable insulator cushion 55 is provided between the battery 43 and the bottom of the compartment of the handle 42.

The operation of the torque wrench illustrated in FIGS. 1-3 will now be described. To set the torque wrench, the operator places the projecting finger 39 of the torque-set arm 30 in a selected aperture of indicator plate 32 This is accomplished by depressing projecting head 38 and pivoting torqueset arm 30. If, in FIG. 1, the work is to be tightened by pulling the handle 42 counterclockwise, i.e., to the left as viewed in FIG. 1, then the wrench is set by placing the finger 39 of the torque-set arm 30 in one of the apertures 35 lying to the right of the pointer 50. In FIG. 1, the torque-set arm 30 is indicated as being set in the first aperture to the right of the pointer.

It will be seen that as the work at the head 10 is tightened by the operator pulling the handle 42 counterclockwise, as viewed in FIG. 1, a condition will develop wherein the head 10 will resist further movement in the counterclockwise direction and thereafter the continued application of force to the forceapplying handle elements 42 and will cause the yieldable beam 20 to bend, and this will carry the indicator plate 30 in an arcuate path in the counterclockwise direction. As a result, the finger 39 will make contact with the pointer and this will complete an electrical circuit and energize the buzzer 44.

The electrical circuit, just referred to, may be traced from the terminal 46 of the battery 43 down through the insulated lead 47 to the soldered connection on the ring terminal 29, then up through the torque-set arm 30, through the finger 39, down the pointer 50, through the head 10, up the beam 20, through the sleeve 40, the handle 42, the cap 45, screw 49, and through buzzer 44 to the other terminal 48 of the battery 43.

As just explained, if the movement of the force-applying handle members 42 and 40 is to be in the counterclockwise direction, as viewed in FIG. 1, the selected value of torque may be set by the operator pivoting the torque-set arm 30 about the pivot stud 23 to such angular position relative to the pointer 50 that the finger 39 projects through a selected one of the apertures 35 of plate 32 which lie to the right of the pointer 50, as viewed in FIG. 1. If the work is to be tightened in the other direction, i.e., if the force-applying elements 40, 42 are to be moved in the clockwise direction, the operator sets the desired torque by moving the torque-set arm 30 pivotally counterclockwise so that the finger 39 projects through a selected aperture lying to the left of the pointer 50, as viewed in FIG. 1. In the illustrated embodiment, the operator, before he can move the torque-set arm 30 pivotally about the stud 23, must press the head 38 rearwardly, relative to plate 32, as indicated in phantom in FIG. 2, until the finger 39 is clear of the plate. He may then pivot the torque-set arm 30 about the stud 23. When the arm 30 is so pivoted, good conductive contact is maintained between the annular end of arm 30 and the terminal ring 29. The maintaining of good electrical contact between elements 29 and 30, while allowing arm 30 to move relative to ring 29, is under the control of nut 34 which is threaded on to the end of stud 23.

The function of the elongated slot 27 in stud 23 should perhaps be explained. This slot facilitates assembly of the device. The insulated wire 47 may be fished down the bore 21 and out of the radial hole 22. Before stud 23 is inserted in hole 22, wire 47 is threaded through the bore 25 and out the end thereof. The stud 23 is then inserted into the beam 20 and tightened by rotation. In its final position, the slot 27 is up, as shown in FIG. 1. The end of the wire 47 is then pushed back into the bore 25 and out of the slot 27.

The apertures 35 in indicator plate 32 may be calibrated to read the torque in foot/pounds or in inch/pounds, or both.

In the embodiment shown in FIGS. 1-3, since the apertures 35 are spaced, the operator is given a step adjustment and hence a step selection of the desired torque force to be applied.

In the embodiment of FIGS. 4 and 5, instead of having a series of apertures, the plate 30 is provided with an elongated arcuate slot 65 through which the finger 39 projects, and through which it may be moved. The arm 30 may be secured in place at its desired angular position, relative to the reference pointer 50, by means of a set screw 68 mounted in the head 38 of the arm 30 and which bears against the outer edge of the plate 32.

FIGS. 6 and 7 represent a modification in that in lieu of having a buzzer 44 as the signalling device, a lamp 60 is used. In this case, the screw cap 61 of the metal handle 42 is a lightpervious plastic insulator material, so that when the lamp 60 becomes illuminated by the closing of the torque-set circuit, the fact that the lamp 60 has been energized will be readily noted by the operator.

FIG. 8 is a schematic diagram of a modification in which signalling is achieved by both a buzzer 44 and also by a lamp 60, these being connected in parallel.

The use of an audible or visual electrically operated signal device, preferably a buzzer, to inform the operator that the desired torque force has been applied to the nut, or bolt, or other work item, should in many cases, result in greater precision. For in many instances, the operator handles the torque wrench in such positions that he cannot readily see the scale, or he may see the scale at such an angle that accurate reading thereof is unlikely. With the present invention, the operator is notified sharply that the desired limit of torque force has been reached thus causing on instantaneous reaction in the operator and immediate release of the applied force. The invention also makes it possible for an operator on a production line to handle quickly and in succession a series of items all requiring application of the same amount of torque force.

In FIG. 6, the member 12 which is adapted to be received within the work-engaging socket S is shown to be pivotal about the pivot pin 65, so that it may extend either forwardly or rearwardly relative to the indicator plate 32 This feature is not needed when the buzzer or other signalling device is operative, since it is unnecessary for the operator to watch the scale on the indicator plate. However, if the battery is worn out or the power supply is otherwise disabled and the tool is being used, as it may be, as a visual reading scale tool, then the reversible feature with respect to the member 12 is useful.

While a battery in the handle has been shown, and is preferred as the power supply for a portable too], there may be installations, such as in volume production, where an external power source may be used, connected to the tool through a suitable cord.

In the embodiments described thus far, the operator sets the contact finger 39 of torque-set arm 30 in that opening 35 in indicator plate 32 which corresponds to the torque force to be applied. The effect of this setting is to space the contact finger 39 from the fixed pointer or reference contact arm 50 by a distance corresponding to the torque force selected to be applied.

In the embodiment shown in FIG. 9, the role of the contact finger and pointer are reversed. In FIG. 9, the pointer is movable pivotably about the work head 10, and the pointer 150 functions as the torque-set arm. The contact finger 139 is held fixed on the yieldable beam 20 and functions as the reference contact. During tightening of the work, as the beam 20 bends, the reference contact finger 139 is carried in an arcuate path toward the torque-set contact arm 150 which has been set by the operator in the desired angular position.

In FIG. 9, one suitable way of making arm 150 pivotally adjustable on the head 10 is illustrated. Other suitable means could, of course, be employed. In FIG. 9, the arm 150 is shown secured to the head 10 by a screw 151 spring-loaded by a spring 152. To set the arm 150 to the desired torque, the

operator merely pulls the lower end of arm 150 outwardly away from the head 10, against the action of the spring 152, and pivots the arm 150 to the desired angular position. When the arm 150 is in its outward position, indicated in phantom in FIG. 9, the upper end of the arm clears the contact finger 139 which is fixed to the upper end portion of the beam 20. The calibrated scale may be placed either on a plate 123 fixed to the beam 20 in the region of the fixed finger 139, or the scale may be placed on the head at the lower or pivotal end of the arm 150.

The type of torque wrench shown in FIG. 9 may be used in the absence of an electrical signalling circuit, without need for the operator to watch the scale. For, when the yieldable beam bends and the fixed contact finger 139 contacts the torqueset arm 150, the arm 150 will function as a stop, thus notifying the operator that the desired torque force has been applied.

The preferred use of the torque wrench of FIG. 9 is, however, with a battery operated signalling circuit. The fixed contact finger 139 is shown mounted on a conductive plate 123 which is secured to, but insulated from, the beam 20 by insulating washers and insulating screws. The dashed line in FIG. 9 represents the insulated electrical lead 47 which runs down the bore 21 at the upper end of the beam 20, out through a radial hole, and is connected to the conductive plate 123. The circuit back to the battery is through the contact finger 139, arm 150, head 10, and beam 20.

What is claimed is:

1. A torque wrench comprising:

a. a yieldable metal beam having at one end work-engaging means, at the other end a force-applying handle;

b. a metal pointer-contact arm connected to said work engaging means and extending in fixed position along the normal axis of said yieldable beam toward said force-applying end;

c. a metal torque-set arm adjustably and pivotally mounted on said beam at the force-applying end;

said torque-set arm carrying a metal contact finger at its free end portion, said finger projecting therefrom in the direction of said pointer-contact arm;

e. an electrically insulated indicator plate fixed to said beam at the force-applying end;

f. said indicator plate having slot means for holding said contact finger in selected positions on either side of said beam normal axis so that by pivotal adjustment of said torque-set arm said contact finger is held to one side or the other of said normal axis at a preselected distance therefrom corresponding to the preselected torque to be applied;

g. electrical circuit means, including said yieldable beam, said pointer-contact arm, said torque-set arm and contact finger, a source of power and a signal device housed within said handle, and an insulated lead connecting the pivotal end of said torque-set arm to said power and signal device;

h. said contact finger and pointer-contact arm remaining apart until the selected amount of torque force is applied, at which time said contact finger contacts said pointercontact arm to close said electrical circuit and energize said signal device.

2. A torque wrench according to claim 1 characterized in that:

a. said slot means in said indicator plate comprises a series of individual apertures disposed in side by side relation along a path through which the contact finger of said torque-set arm is adapted to move;

b. said torque-set arm is resilient to allow said contact finger to be withdrawn from, and to be inserted into, any selected one of said apertures. 

1. A torque wrench comprising: a. a yieldable metal beam having at one end work-engaging means, at the other end a force-applying handle; b. a metal pointer-contact arm connected to said work engaging means and extending in fixed position along the normal axis of said yieldable beam toward said force-applying end; c. a metal torque-set arm adjustably and pivotally mounted on said beam at the force-applying end; d. said torque-set arm carrying a metal contact finger at its free end portion, said finger projecting therefrom in the direction of said pointer-contact arm; e. an electrically insulated indicator plate fixed to said beam at the force-applying end; f. said indicator plate having slot means for holding said contact finger in selected positions on either side of said beam normal axis so that by pivotal adjustment of said torqueset arm said contact Finger is held to one side or the other of said normal axis at a preselected distance therefrom corresponding to the preselected torque to be applied; g. electrical circuit means, including said yieldable beam, said pointer-contact arm, said torque-set arm and contact finger, a source of power and a signal device housed within said handle, and an insulated lead connecting the pivotal end of said torque-set arm to said power and signal device; h. said contact finger and pointer-contact arm remaining apart until the selected amount of torque force is applied, at which time said contact finger contacts said pointer-contact arm to close said electrical circuit and energize said signal device.
 2. A torque wrench according to claim 1 characterized in that: a. said slot means in said indicator plate comprises a series of individual apertures disposed in side by side relation along a path through which the contact finger of said torque-set arm is adapted to move; b. said torque-set arm is resilient to allow said contact finger to be withdrawn from, and to be inserted into, any selected one of said apertures. 